Alto aComp User manual

Brand: Alto

Model: aComp

Category: Supplementary music equipment

Type: User manual

Alto aComp is a 24/32-bit digital compressor module with a robust and compact design. It features a 24/32-bit digital audio processor, MPU control, and automatic bypass switch detection. The Alto aComp has 16 great-sounding programs, a variation adjust knob with 16 positions, an analog "process bypass" switch, and variable input and output gain. It also includes stereo/mono jack inputs, an illuminated power switch, and a digital saturation LED. With up to 9dBu line level and easy-to-operate front panel controls, the Alto aComp is a powerful and versatile tool for audio processing.

24 32 Bit Digital Compressor

Module

User's Manual

LTO

www.alto proaudio.com

Version 1.0 April 2002

English English

Comp

ON OFF

SAFETY RELATED SYMBOLS

CAUTION

RISK OF ELECTRIC SHOCK

DO NOT OPEN

This symbol, wherever it appears,

alerts you to the presence of

uninsulated dangerous voltage

inside the enclosure-voltage that

may be sufficient to constitute a

risk of shock.

This symbol ,wherever it appears ,

alerts you to important operating

and maintenance instructions in

the accompanying literature .

Read the manual .

Protective grounding terminal .

Alternating current /voltage .

Hazardous live terminal .

ON: Denotes the apparatus turns on .

OFF: Denotes the apparatus turns off ,

because of using the single pole switch ,

be sure to unplug the AC power to

prevent any electric shock before you

proceed your service .

WARNING: Describes precautions

that should be observed to prevent the

danger of injury or death to the user .

CAUTION: Describes precautions that

should be observed to prevent danger

of the apparatus .

WARNING

Power Supply

Ensure the source voltage matches

the voltage of the power supply before

turning ON the apparatus.

Unplug this apparatus during lightning

storms or when unused for long periods

of time .

External Connection

The external wiring connected to the

output hazardous live terminals requires

installation by an instructed person, or the

use of ready-made leads or cords.

Do not Remove any Cover

There are maybe some areas with high

voltages inside, to reduce the risk of electric

shock, do not remove any cover if the power

supply is connected.

The cover should be removed by the

qualified personnel only.

No user serviceable parts inside.

Fuse

To prevent a fire, make sure to use fuses

with specified standard (current, voltage,

type). Do not use a different fuse or short

circuit the fuse holder.

Before replacing the fuse, turn OFF the

apparatus and disconnected the power

source.

Protective Grounding

Make sure to connect the protective

grounding to prevent any electric

shock before turning ON the app-

aratus.

Never cut off the internal or external

protective grounding wire or dis-

connect the wiring of protective

grounding terminal.

Operating Conditions

This apparatus shall not be exposed

to dripping or splashing and that no

objects filled with liquids, such as

vases, shall be placed on this apparatus.

To reduce the risk of fire or electric

shock, do not expose this apparatus

to rain or moisture.

Do not use this apparatus near water.

Install in accordance with the manufacturer's

instructions. Do not install near any heat

sources such as radiators, heat registers,

stoves, or other apparatus (including am-

plifiers) that produce heat. Do not block

any ventilation openings.

No naked flame sources, such as lighted

candles, should be placed on the apparatus.

IMPORTANT SAFETY INSTRUCTIONS

Read these instructions.

Keep these instructions.

Heed all warnings.

Only use attachments/accessories

specified by the manufacturer.

Power Cord and Plug

Do not defeat the safety purpose of

the polarized or grounding type plug.

A polarized plug has two blades with

one wider than the other. A grounding

type plug has two blades and a third

grounding prong. The wide blade or

the third prong are provided for your

safety. If the provided plug does not

fit into your outlet, consult an elec-

trician for replacement of the obsolete

outlet.

Protect the power cord from being

walked on or pinched particularly at

plugs, convenience receptacles, and

the point where they exit from the

apparatus.

Cleaning

When the apparatus needs a cleaning,

you can blow off dust from the apparatus

with a blower or clean with rag etc.

Don't use solvents such as benzol,

alcohol, or other fluids with very strong

volatility and flammability for cleaning

the apparatus body.

Clean only with dry cloth.

Servicing

Refer all servicing to qualified personnel.

To reduce the risk of electric shock, do not

perform any servicing other than that

contained in the operating instructions

unless you are qualified to do so .

Servicing is required when the apparatus

has been damaged in any way ,such as

power supply cord or plug is damaged ,

liquid has been spilled or objects have fallen

into the apparatus, the apparatus has been

exposed to rain or moisture, does not operate

normally, or has been dropped.

Follow all instructions.

Preface

Dear Customer,

Thanks for choosing LTO Comp and thanks for choosing one of the

results of

LTO

AUDIO TEAM job and researches.

We have been designing professional audio products for a long time in cooperation

with some of the major brands in the world in the audio field.

The LTO line presents unparalleled analogue and digital products made by

Musicians for

Musicians in our R&D Centers in Italy, Netherlands, United Kingdom

and Taiwan. The core

of our digital audio products is a sophisticated DSP (Digital

sound processor) and a large

range of state of the art algorithms which have been

developed by our Software Team for the Last 7 years.

Because we are convinced you are the most important member of LTO AUDIO

TEAM and

the one confirming the quality of our job, we'd like to share with you our

work and our dreams,

Paying attention to your suggestions and your comments.

Following this idea we create our products and we will create the new ones! From

our side,

we guarantee you and we will guarantee you also in future the best quality,

the best fruits

of our continuous researches and the best prices.

Our LTO Comp is the result of many hours of listening and tests involving

common people, area experts, musicians and technicians.

Nothing else to add, but that we would like to thank all the people that made the

LTO

Comp a reality available to our customers, and thank our designers

and all the LTO staff,

there to make possible the realization of products

containing our idea of music and sound

and there to support you , our customers,

in the best way, conscious that you are our best richness.

Thank you very much.

LTO AUDIO TEAM

For our LTO AUDIO TEAM, music and sound are more than a job ....are first of

all passion

and let us say ...our obsession!

The result of this effort is the realization of dynamic process presets ,useful for

complex sound sources as CD or for single instruments sound improvement,

collected and transformed in presets now available in our small (half rack space),

efficient and easy to use LTO Comp.

Table of Contents

1. Introduction ...........................................................................................6

2. Feature List ............................................................................................6

3. Front and Back Panels description .........................................................6

3.1 Control Panel (Front Panel)

a. Program and Variations Selections

b. Analog Levels

c. LED and Illuminated Power Switch

3.2 Analog Connections (Back Panel)

a. Analog Inputs/Outputs

b. Compressor Bypass Pedal Input

c. Power Connector

4. Installation & Connection .......................................................................8

4.1 Audio Connections and Power Up

a. Audio Connections

b. Power Up Setting

4.2 Analog

a. Input Jack Wiring

b. Levels Setting

c. Compression Process Bypass

4.3 Installation

a. Standard Use

b. Application Examples

-Line Instrument

-Mixer

4.4 Rackmount

5. Preset Functions Descriptions ...............................................................12

5.1 Stereo AGC

5.2 Dynamic Compression Process

5.3Stereo 2 Bands Compressor

e. classic 5

f. classic 6

g. classic 7

h. classic 8

5.7 Compression Effects Summary Table

6. Technical Specifications .....................................................................18

6.1 Block Diagram

6.2 Specifications

7 Warranty ...............................................................................................20

a. classic 1

b. classic 2

c. classic 3

d. classic 4

5.6 Mono 2 Bands + 5 Bands Eq Compressor Presets

5.4 Stereo 2 Bands Compressor Presets

a. agc pure

b. acoustic

c. master

d. clean

e. dance

f. kick drum

g. mixdown

h. jumping up

5.5 Mono 2 Bands + 5 Bands Eq Compressor

1. Introduction

Purchasing LTO Comp, you purchased a very powerful dynamic processor,

easy to

use and contained in a very efficient half rack package.

LTO Comp is divided in two

groups of 8 compression algorithms and

16 AGC configurations for each of these algorithms.

The first 8 compression algorithms have been designed for a general purpose use

and very powerful when processing "full band" input signals as CD sources or as

final results of mixing sessions. These algorithms are fully stereo algorithms and do

not introduce heavy modifications in sound's colour.

The second 8 algorithms have been designed for the processing of mono signals

and mono sound sources as musical instruments or voice. These algorithms may

change quite heavily the colour and the phase of the input signal, so as the balance

between low and high frequencies of the signal itself.

All the algorithms are based on classical algorithms for the dynamic compression

of audio signals, modified and optimized thanks to the experience of LTO AUDIO

TEAM researchers.

2. Feature List

Robust and Compact design

24/32 bits Digital Audio Processor

MPU Control

Automatic Bypass Switch Detection

16 Great Sounding Programs

Variation Adjust Knob (16 positions)

Analog "Process Bypass" Switch

Variable Input / Output Gain

Stereo/Mono Jack inputs

Illuminated Power Switch

Digital Saturation Led

Up to 9dBu Line Level

Easy to Operate Front Panel Controls

SMT Design for Greater Reliability

Short Signal Path and no Internal Cabling to Provide Superior Sound

Manufactured Under ISO9001 Quality system

3. Front and Back Panels Description

3.1 Control panel (Front Panel)

- Analog Output Level Potentiometer : The output level control sets the level

going to the

amplifier or mixer from this apparatus.

- "Process Bypass" Switch: The "Process Bypass" switch allows to bypass the

digital process so to have the input signal available on the outputs.

c. LED and Illuminated Power Switch

- Digital Saturation LED : Displays the signal level coming into the input during

normal operation, if the signal level is too high, this LED will light and you will

begin to hear the signal distortion.

- Power On/Off Switch : Turns the apparatus on and off.

3.2 Analog Connections (Back Panel)

-Analog Input Level Potentiometer : The input level control sets the main input

gain, before

the signal reaches the input bus. It controls both the Left ( Mono)

and Right input levels

simultaneously.

b. Analog Levels

a. Program and Variations Selections

- Program Select Knob: The Program Select Knob is used to choose the program

you wish to perform.

- Variations Select Knob : Each program on this apparatus has the AGC parameter

which can

be adjusted by means of this knob.

a. Analog Inputs/Outputs

- Inputs : These are 1/4" unbalanced phone jacks which connect to sources

such as Channel inserts of a mixing console. They may be used with Line

input levels up to 8/9 dBu. For mono application, use the Left / Mono input.

The Left / Mono input jack is normal to the Right jack. This means that when nothing

is plugged into the Right input jack, the signal present at the Left / Mono input is

routed to the Right as well.

9 VAC~

POWER

BYPASS

OUTPUT

INPUT

LEFT RIGHT LEFT(MONO) RIGHT

SIGNAL

OUTPUT

INPUT

243 2 bit Digital Compressor Module

10 0 10

MASTER

MIXDOWN

JUMPING UP

DANCE

CLEAN

KICK DRUM

ACOUSTIC

AGC PURE

VARIATIONS

POWER

CLASSIC 8

CLASSIC 7

CLASSIC 6

CLASSIC 5

CLASSIC 4

CLASSIC 3

CLASSIC 2

CLASSIC 1

Comp

LTO

COMP

BYPASS

ON OFF

Do not place cables where they can be stepped on.

Avoid twisting a

cable

or having it make sharp right angle turns.

b. Power Up Setting

Before turning on the Comp's power, check if:

All connections have been made correctly.

The volume controls of the amplifier or mixer are turned down.

Insert the Power plug into the [POWER] input on the rear panel of the Comp

Always unplug cables by firmly grasping the body of the plug and pulling directly

outward.

Do not bundle audio cables with AC power cords.

Do not place audio cables and Comp near sources of

electromagnetic

interference such as transformers, monitors, computers, etc.

- Outputs : These are 1/4" unbalanced phone jacks which connect to devices

such as the

channel inserts on a mixing console or power amplifier inputs.

b. Compressor Bypass Pedal Input

- Compressor Bypass : This is a 1/4" phone jack which connects to a footswitch

( with

latching ), either normally-open or normally-closed. When the footswitch

is in the state of

" OFF ", the function will be " Compressor "; On the other hand,

when the footswitch is in the

state of " ON ", the function will be " Bypass ".

c. Power Connector

- Power connector : This is a plug for connecting the 9VAC power supply adapter

provided

by the manufacturer.

4. Installation & Connection

4.1. Audio Connections and Power Up

a. Audio Connections

Turn on the power of the amplifier/mixer, and adjust the volume.

Turn on the power of the Comp, pushing the ON/OFF button on the front panel.

and plug the power adapter into an AC outlet.

The connections between the Comp and the other audio devices have to be made

using high quality cables so to prevent bad performances of the Comp itself.

So it should be good to use low-capacitance shielded cables with a flexible

internal conductor. Connect the cables to the Comp properly by observing

the following precautions:

4.2. Analog

a. Input Jack Wiring

The Comp's LEFT INPUT jack is also mono input for the Comp. If

you only connect a single mono cable to the LEFT INPUT jack, it will be

through the

Comp unchanged. This can be done in two ways:

by pushing the BYPASS switch

by connecting a footswitch to the BYPASS jack and pressing the footswitch.

On the back panel you will find a footswitch jack labelled BYPASS . This is a mono

jack with

connections for a standard footswitch. The footswitch must be plugged

in before

the Comp has its power turned on: Comp will automatically

recognise

the right "polarity" of the pedal.

4.3 Installation

a. Standard Use

The Comp may be placed almost anywhere on a table, on top of an amp,

next to a mixing console. If it will be on furniture, check the rubber feet provided

b. Levels Setting

Proper setting of the input and output levels is crucial in order to achieve the maximum

signal-

to-noise ratio. It is possible to say that it is usually best to set both input

and output level

controls at 3/4 or 75% of full. This will decrease the possibility

of overload distortion and

keep the amount of background noise to a minimum.

c. Compression Process Bypass

At any time you can bypass the process, there by allowing the direct signal to pass

also routed automatically to the RIGHT INPUT. However , if we are using

stereo input signals, connecting a cable to the RIGHT INPUT jack , the

automatic routing will be avoided and the LEFT INPUT jack will feed only

the LEFT INPUT, and the RIGHT INPUT jack will feed only the RIGHT INPUT.

If the Signal LED on the Comp start lighting, signaling a process saturation,

turn down the Input level or decrease the volume of the source (instrument,

mixer send, etc.). If the Comp's level is causing the mixer or amp to distort,

turn the Output Level down.

to the bottom of the unit. Make sure to place the Comp's power supply away

from other audio equipment that may induce fields, and away from the signal wiring.

It is possible that Comp may pick up noise field generated by other equipment

such as large power amplifiers; in this case, move the Comp until the noise goes

away.

When connecting audio cables and/or turning power on and off, make sure that

all devices in your system have their volume controls turned down.

The Comp has two 1/4" unbalanced inputs and two 1/4" unbalanced outputs.

These input /output configuration may provide three different audio connections

options:

MONO. Connect an audio cable to the [LEFT] INPUT of the Comp from

a mono

source, and another audio cable from the [LEFT] output of the

Comp to an

amplification system or mixer input.

To Amplifier or Mixing

Console

From Instrument or Mono Audio Source

Left Output

Left Input

Amplifier or

Mixing

Console

Right Output

Left output

Left Input

MONO IN, STEREO OUT. While still using the LEFT mono input, you could

connect two

audio cables to the LEFT and RIGHT outputs of the Comp to

a stereo

amplification system or two mixer inputs.

b. Application Examples

line instrument

STEREO. Connect two audio cables to the LEFT and RIGHT INPUTS of the Comp

from a stereo source , and two other audio cables cords from the LEFT and

RIGHT OUTPUTS

of the Comp to a stereo amplification system or two mixer

inputs.

SIGNAL

OUTPUT

INPUT

243 2 bit Digital Compressor Module

10 0 10

MASTER

MIXDOWN

JUMPING UP

DANCE

CLEAN

KICK DRUM

ACOUSTIC

AGC PURE

VARIATIONS

POWER

CLASSIC 8

CLASSIC 7

CLASSIC 6

CLASSIC 5

CLASSIC 4

CLASSIC 3

CLASSIC 2

CLASSIC 1

Comp

LTO

COMP

BYPASS

SIGNAL

OUTPUT

INPUT

243 2 bit Digital Compressor Module

10 0 10

MASTER

MIXDOWN

JUMPING UP

DANCE

CLEAN

KICK DRUM

ACOUSTIC

AGC PURE

VARIATIONS

POWER

CLASSIC 8

CLASSIC 7

CLASSIC 6

CLASSIC 5

CLASSIC 4

CLASSIC 3

CLASSIC 2

CLASSIC 1

Comp

LTO

COMP

BYPASS

ON OFF

mixer

Interfacing to a Mixing Console

The Comp can accept mono or stereo sends at all system levels. The input circuitry

of the

Comp can easily accept professional +8/9 dBu levels while having

Enough input

And output gain to interface with the low signal levels of

recording systems.

The Comp may be connected to a mixing console connecting the unit directly

to the

channel insert socket of a single channel that is to be processed.

Another way of

interfacing the Comp to a mixer or recording console would

be in-line between the

output of your mixing console and the input of a tape

deck or power amplifier. This last setup

would be used only if you wanted

to process the entire mix.

Using Inserts

MIXING CONSOLE

Insert

Left

Input

Left

Output

In the above figure it is described the situation in which you want to apply the

To Amplifier or Mixing

Console

Right Output

Left output

Right Input

From Stereo Audio Source

Left Input

Comp to apply the desired dynamic process to single instrument's signals;

in this case

you will have to use a mixer which

features individual channel

inserts. Insert

jacks on the back of a mixer provide a way of

'inserting'

external processing

equipment into the signal path. The insert occurs after the

input amplifier, and

before the channel fader; essentially it is the same as

connecting the

source

(instrument or mic) into the Comp before the mixer's

channel input. Usually,

insert connections require a special, stereo-splitting

Y-cord to be connected, known

as TRS

connector. This connector has a stereo

jack which plugs into mixer's

channel insert socket,

and a couple of mono jacks

(input and output) which will

plug into Comp. Fitting this

kind of adapters

will virtually insert into one

mixer's channel the compression processing.

home

SIGNAL

OUTPUT

INPUT

24 32 bit Digital Compressor Module

10 0 10

MASTER

MIXDOWN

JUMPING UP

DANCE

CLEAN

KICK DRUM

ACOUSTIC

AGC PURE

VARIATIONS

POWER

CLASSIC 8

CLASSIC 7

CLASSIC 6

CLASSIC 5

CLASSIC 4

CLASSIC 3

CLASSIC 2

CLASSIC 1

Comp

LTO

COMP

BYPASS

SIGNAL

OUTPUT

INPUT

243 2 bit Digital Compressor Module

10 0 10

MASTER

MIXDOWN

JUMPING UP

DANCE

CLEAN

KICK DRUM

ACOUSTIC

AGC PURE

VARIATIONS

POWER

CLASSIC 8

CLASSIC 7

CLASSIC 6

CLASSIC 5

CLASSIC 4

CLASSIC 3

CLASSIC 2

CLASSIC 1

Comp

LTO

COMP

BYPASS

ON OFF

5. Preset Functions Descriptions

5.1 Stereo AGC

The Comp's dynamic process algorithm includes also a stereo Auto-

matic

Gain Control (AGC) "block" that, if used, is able to maintain almost

stable during the time the mean amplitude of the input signal, increasing it

when the "average"of the input signal amplitudes seems to be low and decreasing

it when the "average" of the input signal amplitude seems to be

too high.

This process is useful when the sound reaching the input of Comp is coming

from different sources having different output levels and it is necessary to

Take good care in adjusting Comp input and output levels, in order to

satisfy the

dynamics needs of both the processed channels. If you don't hear

any sound, try to swap

the Input and Output ends of the TRS cable plugged into

the Comp. Do not use for the

Comp the effects send/return connections

found on

most mixers for effect modules,

as they could lead to heavy frequency

response

alterations.

MONO IN

If you only want to use Comp for a mono input signal and to connect both of

its outputs

back to the mixer, you will need three audio cables. Connect a

channel insert from the

console to LEFT mono input of the Comp via TRS,

and another audio cable

from the LEFT or RIGHT output of the

Comp to

an adjacent mixer input.

STEREO IN - STEREO OUT.

This connection is similar to the one described above. However, by utilizing two

TRS and

console channel inserts, we can process a couple of signals or a stereo

signal coming ie.

This operation mode is the one used with the

algorithms from 1 to 8, designed

from a keyboard.

to process

audio stereo sources as CD.

Improper level setting when using a dynamic processor is the most common cause

of noise and distortion problems

4.4 Rackmount

The most secure mounting is on an "universal" rack shelf, available from

various rack

manufacturers or music dealer.

Up to two Comp's may be

mounted

side-by-side in a standard universal

EIA 19" equipment rack.

the dynamic process operating as "second block" of the algorithm.

"NORMALIZE" the input level of the Comp to obtain better performances from

SIGNAL

OUTPUT

INPUT

24 32 bit Digital Compressor Module

10 0 10

MASTER

MIXDOWN

JUMPING UP

DANCE

CLEAN

KICK DRUM

ACOUSTIC

AGC PURE

VARIATIONS

POWER

CLASSIC 8

CLASSIC 7

CLASSIC 6

CLASSIC 5

CLASSIC 4

CLASSIC 3

CLASSIC 2

CLASSIC 1

Comp

LTO

COMP

BYPASS

SIGNAL

OUTPUT

INPUT

24 32 bit Digital Compressor Module

10 0 10

MASTER

MIXDOWN

JUMPING UP

DANCE

CLEAN

KICK DRUM

ACOUSTIC

AGC PURE

VARIATIONS

POWER

CLASSIC 8

CLASSIC 7

CLASSIC 6

CLASSIC 5

CLASSIC 4

CLASSIC 3

CLASSIC 2

CLASSIC 1

Comp

LTO

COMP

BYPASS

ON OFFON OFF

2.Compressor Speed: This parameter represents the speed with which the

signal is

compressed once it goes beyond the Compressor Threshold. This

is true only if the Min

value is different from 0dB.

4.Compressor Threshold: This is the threshold beyond which the signal is

compressed.

5.Hold Threshold: When this threshold is crossed by the signal level, coming

from the

compression region, the compression coefficient is maintained steady.

When the

crossing

is from the expansion region, then is the expansion coeff-

icient

that is

kept the same.

6.Max: This is the maximum expansion ratio between input and output in the

expansion region.

7.Min: This is the maximum compression ratio between input and output in the compre-

ssion region.

The AGC = Const. areas are regions where the multiplying coefficient value

assumes the

last calculated before crossing the different thresholds, so in the expansion area

the COEF

agc value is increasing, while in the compression area the COEF agc

value is decreasing.

As the name implies , compression reduces the dynamic range of a signal. It is

used extensively in audio recording, production work , noise reduction, and live

performance applications, but it does need to be used with care.

A compressor is basically a variable gain device, where the amount of gain used

depends on the level of the input. In this case, the gain will be reduced when the

signal level is high which makes louder passages softer, reducing the dynamic

range.

5.2 Dynamic Compression Process

3.Expander Threshold: Expander Threshold is the threshold beyond which the

signal is

expanded.

1.Expander Speed: The parameter Expander Speed represents the speed with

which the

signal is expanded beyond the Expander Threshold, this is true only

if the Max value is

different from 0dB.

OUTPUT

Compressor Ratio

Max Level

AGC Coet = Decreased = f(Comp Speed)

Threshold Comp

Threshold Hold

Threshold Exp

Input

AGC Coef = Constant

AGC Coef =increment = f(Exp Speed)

AGC Coef =Constant

AGC Coef Min = f(Cmp Ratio)

AGC Coef Max = f(Exp Ratio)

Exp Ratio

5.3 Stereo 2 Bands Compressor

The Comp's Stereo 2-bands dynamic process algorithm is based on a "multi-

band" process concept, splitting the full band of the input signals in 2 "sub-bands"

the low frequencies band and the mid/high frequencies band, so to be able to

differentiate the dynamic processes operating on the low frequencies (with higher

energy content) and on the mid/high frequencies (with lower energy content).

This technique allows to avoid the well know "pumping" effect appearing often

when operating a dynamic process on sound signal.

Once splitted the input signal in 2 "sub-bands", Comp operate a first limiting

process on the low frequencies band, and after, once recreated the full band,

apply a powerful stereo dynamic process on the two "recombined" channels.

A compressor's input/output relationship is often described by a simple graph:

The horizontal axis corresponds to the input signal level, and the vertical axis

is the output level (both measured in decibels) . A line at 45 degrees corresponds

to a gain of one - any input level is mapped to exactly the same output level.

The compressor changes the slope (makes it more horizontal) of that line

above some value called the threshold (which is most often adjustable). The height

of the line defines the dynamic range of the output

and the slope of that line is the

same as the compressor's gain.

Input

Output

Level

Detector

Gain

Control

Left

Stereo AGC

Right

ON/OFF

LPF

HPF

Limiter

Vol1

Vol2

Vol3

Vol4

Left

Right

Stereo

Compressor

Limiter

This kind of dynamic process is very useful for the dynamic control of complex

sounds as the ones coming from CD or orchestras etc.

a. Agc pure

This process is a simple automatic level control. Its speed varies with the different

'variation'

control positions. From the timbre point of view it's a rather neutral

process, and it doesn't

alter the general balance of the original signal. It simply

keeps the level in proximity of a fixed

level, correcting the source variations. It

can be noticed that variation 1 disables the AGC. It does so even in the compressor

presets.

This variation can be considered a sort of bypass.

b. Acoustic

The general impression this preset gives is of definition and power. The timbre is

lively and

brilliant, ideal for small ensemble music and to keep live soft passages.

5.4 Stereo 2 Bands Compressor Presets

c. Master

Master is very neutral and it is usable as a hi-performance AGC. It can be put before

power

amps and recorders in order to optimize their dynamic range. Timbre is very

Frequency response

is slightly rolled off in the low end.

similar to original

signals' and so the unique appreciable differences are in the

dynamic range corrections.

variations 2 through 16 activate even the AGC to help

compressor action.

d. Clean

This is a high definition preset, giving great brilliance and dynamic impression.

Nevertheless

it is never fatiguing and 'pushes' the sound without unbalancing it.

Highs in good evidence,

punch range in good evidence, too, lows not too attenuated.

Good to underline female voices details.

e. Dance

With this program, medium range and mid-low region are well in evidence,

while high

frequencies are slightly attenuated in order to control dance music

intrinsic brilliance in this

region. Well suited to match dynamic and brilliant

recordings, while increasing their "punch".

f. kick drum

In this preset, mid-low region very well in evidence, while high and mid

frequencies are

slightly attenuated. Special preset extremely well suited for drum

recordings. It makes an

excellent work in underlining drums low range in multitrack

recordings or mixed microphones

environments.

g. Mixdown

Mixdown is less brilliant than Clean Preset and has mid-low end more in evidence.

Good

underlining bass and drums without losing definition in the rest of the range.

Suited even for

harmonically complex instruments, like double bass, which have

a non negligible high

frequency range.

h. jumping up

The sound of Jumping Up Preset is quite similar to Clean Preset as general timbre,

but this

preset underlines very well male voices and is capable to keep up the level

in soft passages

of the music program. For female voices the Clean Program is

probably better.

The Comp's Mono 2 Bands+5 Bands Eq dynamic process algorithm is based

on a "multi-band" process concept, splitting the full band signal entering the

dynamic process algorithm in 2 "sub-bands" , the low frequencies band and the

mid/high frequencies band, so to be able to differentiate the dynamic processes

operating on the low frequencies (with higher energy content) and on the mid/

high frequencies (with lower energy content).

This technique allows to avoid the well known :"pumping" effect appearing oftenly

when operating a dynamic process on sound signal.

Once splitted the input signal in 2 "sub-bands", Comp operates a first separate

limiting process on the low frequencies band and on the mid/high frequencies,

and after, once recreated the full band, applies a powerful stereo dynamic processor

on the "recombined" channel.

The input signal to the dynamic compression "block", is the sum of the input

signals filtered with a 5 bands parametric Eq.

This feature allows to modify the "colour" of the input signal before to operate

the dynamic process on it.

5.5 Mono 2 Bands + 5 Bands Eq Compressor

a. Classic 1

5.6 Mono 2 Band +5 Bands Eq Compressor Presets

All the presets made using the above algorithms, and named:

This kind of dynamic process is very useful for the dynamic control of instruments

or "single" sounds.

b. classic 2

c. classic 3

d. classic 4

e. classic 5

f. classic 6

Left

Vol1

Mono

Compressor

Mono

Compressor

LPF

HPF

5PEQ

Mono AGC

ON/OFF

Left

Right

Vol2

Right

Stereo

Compressor

g. classic 7

h. classic 8

LIMITER

band split [Hz]

Limiter Low

Band [dB]

Volume Low

Band [dB]

Volume High

Band [dB]

AGC PURE

800 0 0 0

ACOUSTIC

2500

-2 2

6,5

MASTER

630

-2

-4,5

CLEAN

3150 -3

DANCE

160

-1,5 6,5

KICK DRUM

250

-1,5

2,5

MIX DOWN

5000

-3

2 2

JUMPING UP

1250

-1 2

5.7 Compression Effects Summary Table

COMPRESSOR

Threshold [dB]

Release [dB/s]

Attack [dB/s]

AGC PURE

- -

ACOUSTIC

-2

111

MASTER

-2

CLEAN

2,5

111

DANCE

-1,5

KICK DRUM

-0,5

137

MIX DOWN

-2

JUMPING UP

-1,5

Classic

1,2,3,4,5,6,7,8

-6

6,5 85,5

AGC

EXP SPEED

[dB/s]

CMP SPEED

[dB/s]

EXP THR

[dB]

CMP THR

[dB]

THR HOLD

[dB]

EXP RATIO

[In:Out]

AGC 1

3,5

-61 -26

-44

1:2

AGC 2

3,5 19,5

-34

-29

-32

1:2

AGC 3

3,5 19,5

-42

-26

-3

1:2

AGC 4

-34

-29

-31

1:2

AGC 5

3,2

-44

-29

-31

1:2

AGC 6

3,3 22,5

-44

-29

-42 1:2

AGC 7

3,2 24,3

-37

-29

-33

1:2

AGC 8

4,1

23 -37

-22

-31

1:2

AGC 9

4,1

23 -37

-27

-31

1:2

AGC 10

4,5

24,3

-37

-27

-30

1:2

AGC 11

4,5

22,5

-44

-27

-29

1:2

AGC 12

5,6

-44

-27 -42 1:2

AGC 13

19,5

-42 -27

-31

1:2

AGC 14

19,5

-34

-27

-30

1:2

AGC 15

-61

-27

-32

1:2

have been made thinking for them an use with single instruments. More, the

presets are well tailored on classic guitars or acoustic instruments, where

different equalizations of the sound can give to the instruments more or less character

and deepness, passing from bright equalizations to warmer ones.

Eq Classic Preset

PEQ 1 PEQ 2 PEQ 3 PEQ 4 PEQ 5

Classic 1

G=1dB; F=75Hz ;

Q=1

G=0dB

G=0,5dB;

F=1KHz ; Q=1

G=0dB

G=1dB; F=12KHz ;

Q=1

Classic 2

G=1dB; F=75Hz ;

Q=1

G=-1dB;

F=600Hz ; Q=5

G=-1dB; F=1KHz ;

Q=1

G=1dB;

F=3,7KHz ; Q=5

G=-1dB;

F=12KHz ;

Q=1

Classic 3

G=1dB; F=75Hz ;

Q=5

G=-1dB;

F=600Hz ;

Q=5

G=-1dB; F=1KHz ;

Q=1

G=-2dB;

F=3,7KHz

; Q=5

G=1dB; F=7KHz ;

Q=5

Classic 4

G=2dB; F=50Hz ;

Q=5

G=-10dB;

F=100Hz ;

Q=5

G=-6dB; F=1KHz ;

Q=1

G=-4,5dB;

F=3,7KHz ; Q=1

G=2dB; F=10KHz ;

Q=5

Classic 5

Classic 6

G=1dB; F=75Hz ;

Q=1

G=-1dB;

F=600Hz ;Q=5

G=-1dB; F=1KHz ;

Q=1

G=1dB;

F=3,7KHz Q=5

G=-1dB;

F=12KHz ;

Q=1

Classic 7

G=1dB; F=75Hz ;

Q=5

G=-1dB;

F=600Hz ; Q=5

G=-1dB; F=1KHz ;

Q=1

G=-2dB;

F=3,7KHz ; Q=5

G=1dB; F=7KHz ;

Q=5

Classic 8

G=2dB; F=50Hz ;

Q=5

G=-10dB;

F=100Hz ; Q=5

G=-6dB; F=1KHz ;

Q=1

G=-4,5dB;

F=3,7KHz ; Q=1

G=2dB; F=10KHz ;

Q=5

6 Technical Specifications

6.1 Block Diagram

1 2 3 4

4321

POWER SUPPLY

VOLTAGE REGULATOR

AC 9V

INPUT

+5V

-5V

Comp

BLOCK

MEM

(

DR AM

)

(

)

DSP

ED0-ED7

(

TMS

DPHA

)

EA0-EA9

AD0-AD7

MPU

PROGRAM

ENCODERA

SO0SI0

OUTPUT R

OUTPUT L

INPUTR

INPUTL

(MONOINPUT)

PJ1

PJ2

FOOT

SWITCH

PJ5

PJ3

PJ4

VARIATIONS

ENCODERB

11.0592MHZ

FOOTSWITCH

CONTROL

INPUT BUFFER&AMPLIFIER

INPUT LEVEL

IN--R IN --LO

STEREO AUDIO CODEC

A/D and D/A CONVERTER

(U6 PCM3001E)

UT-RO

CLOCK DIVIDE

(U7 74HC393)

COMP/BYPASS CONTROL

OUTPUT AMPLIFIER

OUTPUT LEVEL

UT-L

LRCKIN=43.20KHZ

BCK= 1.382MHZ

DIAGRAM

(U9 P 7C54UBAA)8

G=1dB; F=75Hz ;

Q=1

G=0dB

G=0,5dB; F=1KHz ;

Q=1

G=0dB

G=1dB; F=12KHz ;

Q=1

6.2 Specifications

Electrical

Frequency Response:

S/N Ratio (process)

S/N Ratio (bypass)

THD+Noise:

Input

Number of Channels:

Format:

Maximum Level (bypass):

Impedance:

A/D - D/A Conversions

A/D converter:

D/A converter:

Output

Number of Channels:

Format:

Maximum Level (bypass):

Output Impedance:

Front Panel

Controls

Indicators

Rear Panel

Input (LEFT/MONO, RIGHT)

Output (LEFT, RIGHT)

BYPASS

Power

Processing and Memory

Processor Speed:

Internal DSP resolution:

Main Preset Programs

Preset Total Combinations

Internal digital audio memory:

Physical

Net Weight:

Dimension:

+0.5 / -1.5 dB from 20Hz to 20 kHz

80 dB "A" wtg, 20 Hz-22kHz

>90 dB "A" wtg, 20 Hz-22kHz

<0.008% @ 1kHz (0dBV, bypass)

1/4" unbalanced

+9 dBu

>500 kOhms

1 bit Sigma-Delta

1/4" unbalanced

+9 dBu

<500 ohms

IN/OUT levels (ANALOG)

PROGRAM selections (2 knobs)

Power, Signal clip LED

1/4" 2-conductor (mono)

1/4" 2-conductor (auto-sense pedal type)

for momentary footswitches

9 Volt AC Power Transformer

12 MIPs (million instructions per second)

52 bit MPY accumulator

256

1kg(2.20lb)

3000 milliseconds

200(W) 150(D) 45(H)mm(7.87" 5.91" 1.77")

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Alto aComp User manual

Brand: Alto

Model: aComp

Category: Supplementary music equipment

Type: User manual

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Alto aComp User manual

Alto aComp User manual

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